Rotary waveguide switch



g- 1963 J. w. GEBHARDT ETAL 3,101,457

ROTARY WAVEGUIDE SWITCH Filed Sept. 28, 1960 INVENTORS' JUL/U5 W. GEBHARDT JOSEPH HENRY [Tr/N651? JOHN H. R/TTENHOUSE United States Patent 3,101,457 RDTARY WAVEGUIDE SWITCH Julius W. Gehhardt, Fresh Meadows, Joseph Henry Ettinger, Flushing, and John H. Rittenhouse, Syosset, N.Y., assignors to Sperry Rand Corporation, Great Neck, N.Y., a corporation of Delaware Filed Sept. 28, 1960, Ser. No. 59,000 Stilaims. (Cl. 333-4) This invention relates to a microwave rotary switch for selectively connecting different pairs of waveguide transmission lines.

Such switches are useful for selectively switching a source of microwave energy between two utilization means such as two antennas, for example, or between an antenna and test apparatus.

A type of rotary switch presently used quite extensively in practice is known as a barrel switch and is comprised of a right-circular cylindrical rotor member having a curved waveguide channel therethrough, and a stator member having a cylindrical cavity or well in which the rotor is housed. The rotor is free to rotate so that the waveguide channel therein selectively connects, or registers with, different pairs of angularly spaced stator waveguide channels. A switch of this type is described in US. Patent 2,705,776. One of the chief matters of concern in a waveguide rotary switch is the R.F. isolation which it provides between selected and nonselected waveguide channels. In order to obtain high isolation in this type of switch it is required that the rotor and stator be assembled with a minimum air gap therebetween, and this requires that they be manufactured with very close tolerances on their physical dimensions. This is difficult and costly, and even with the best manufacturing procedures, appreciable air gaps usually exist between external surfaces of the rotor and the internal surfaces of the stator. This air gap between the rotor and stator members allows microwave energy to leak therebctween, thus giving rise to poor isolation at a nonselected waveguide channel in the stator member. In attempting to overcome this leak-age problem chokes have been employed to suppress the leakage energy. The switch described in the above-mentioned patent is of this type. These chokes are frequency sensitive because they have a critical electrical length, and therefore, the bandwidth of operation of a switch employing these chokes is limited. If a microwave system employing such a type switch is expected to operate over an appreciable frequency range, several switches having different frequency response characteristics must be provided.

Because of the high cost involved in producing a high isolation switch having close mechanical tolerances it has become standard practice to use one type of switch where the'isolation requirements are very high and to use a different type of switch having more liberal mechanical tolerances, and thus less expensive to manufacture, where the isolation requirements are less rigid. This complicates the manufacturing and supplying problem and requires the user to stock a variety of different switches.

Attempts have been made to overcome the above-mentioned difficulties by providing a switch having a tapered rotor that is spring-loaded into intimate contact over at least portions of its tapered surface with a similarly tapered cavity or well in the stator member. A switch of this type is shown in US. Patent 2,556,869. Because the members are urged into intimate contact by the spring loading, it is necessary to have additional mechanisms for separating the two before the rotor may be rotated to a different angular position. This complicates the switch, increases its cost and slows down its switching time.

It therefore is an object of this invention to provide a. rotary 'waveguide switch having high RF. isolation be- 3 1%,457 Patented Aug. 20, 1963 ice tween selected and nonselected waveguide channels, while at the same time having a low voltage standing wave ratio in the selected channels.

It is another object of this invention to provide a rotary waveguide switch for operation over an extremely wide microwave frequency range.

Another object of this invention is to provide a rotary waveguide switching having superior electrical characteristics and which is simple to construct and economical to manufacture.

A still further object of this invention is to provide a relatively small and compact waveguide rotary switch.

Another object of this invention is to provide a rotary waveguide switch which readily may be adjusted to provide substantially any desired isolation within wide limits between selected and nonselected waveguide channels.

Another object of this invention is to provide a rotary waveguide switch having selectable electrical characteristics.

A further object is to provide a waveguide switch which is made of interchangeable parts which readily may be mass produced.

These and other objects of the invention, which will become more apparent from the description and claims below, are achieved by providing a rotor member having sloping sides, that is, frusto-conical in shape, and a stator member having a similarly shaped cavity or Well portion. The stator member has a plurality of radially extending waveguide channels angularly disposed about its periphery and opening on said cavity, and said rotor member has a curved waveguide channel extending therethrough so that at different predetermined angular positions of saidrotor its waveguide channel will register with different pairs of stator waveguide channels. The rotor member is rigidly held in axial position so as to provide a very thin air gap between said rotor and stator members. The means which rigidly holds said rotor member in axial position is, however, axially adjustable so that the air gap between said rotor. and stator members may be readily adjusted. Said axial supporting means further permits extremely lowfriction rotation of said rotor member within said stator member.

For a more detailed description of the novel waveguide switch of this invention reference will be made to the accompanying drawings, wherein:

FIGS. land 2 are, respectively, elevational and horizontal cross-sectional views of an embodiment of the switch of this invention; and

FIG. 3 is a schematic illustration of another embodiment of the rotary waveguide switch which may be constructed according to the present invention.

Referring now more particularly to FIGS. 1 and 2, the switch is comprised of a rotor member 10 having circularly-shaped top and bottom portions 11 and 12, and a rotor member 10. A stem 15, having a flat top surface,

extends upwardly from the top surface 11 of rotor lti.

Stator member 16 is centrally aperturedwith the upper portion of said aperture being fr'usto-conically shaped. The sloping surface 17 of said aperture has an angle of inclination substantially the same as the sloping surface of rotor 10. Radially extending waveguide channels 18, 19 and 213 are angularly positioned about stator 16. The curved waveguide channel 14 of rotor 10 is adapted to register with different pairs of stator waveguide channel 182ll when rotated to d-iiferent angular positions.

A top cover member 21 encloses the top position of stator 16 and is secured thereto by means of screws 22 positioned about the periphery of cover member 21. Cover member 21 is apertured at 23 to permit the free passage therethrough of stem of rotor iii. A neck portion 24 is attached to and extends upwardly from cover member 21 and connects to an internally-threaded portion 25 which is adapted to receive top adjusting screw 26.

A drive arm 27 is secured to stem 15 by means of set screw 23 and provides means for rotating rotor member 19 in response to some driving means not illustrated. The bottommost apertured portion of stator 16 is threaded at '29 to receive bottom adjusting screw 30. Both the top and bottom adjusting screws 26 and 30 are provided with centrally-located comically-shaped bearing surfaces 31 and 32 into which the respective balls 33 and 34 ride to provide ball bearing supports for rotor 10.

Annular discs of material dissipative to microwave energy 35 and 36 respectively are positioned on the top and bottom surfaces of rotor 16 to attenuate microwave energy which leaks through the air gap separating rotor 10 and stator 16. Annular discs 35 and 36 may be made of any of the well-known materials used for this purpose.

As illustrated in FIGS. 1 and 2, the waveguide channel 14 in rotor member .10 has a ninety degree bend and stator member 16 is illustrated as having three waveguide ports which are angularly separated by ninety degrees. This is but one illustrative embodiment of a waveguide switch and is not intended to be a limitation of the present invention. Other arrangements of waveguide ports may be employed equally well, such as the arrangement illustrated in FIG. 3 wherein rotor it) is provided with two curved waveguide channels 40 and 41, and stator 16 is provided with four waveguide channels 42, 43, 44 and 45. Many other arrangements of waveguide channels in rotary switches may be employed in a switch constructed according to the present invention.

In the manufacture and assembly of the switch illustrated in FIGS. 1 and 2, rotor member ill initially would be assembled so as to be bottomed in stator member 16, that is, in its lowermost position with its tapered lateral surface 13' contacting the adjacent tapered surface 17 of stator member 16. Adjusting screws 26 and 30- would be turned inwardly so that balls 33 and 34 would make firm contact with the respective fiat surfaces of stem 15 and bottom portion 12 of rotor 10 without causing said rotor to become disengaged from said stator. The switch then would be inserted in a microwave test system which is capable of measuring the RF. isolation of the nonselected arm or arms of the switch, and the insertion loss and voltage standing wave ratio (V.S.W.R.) in the selected channels. The top and bottom adjusting screws 26 and 30 then are simultaneously turned outwardly and inwardly, respectively, to raise rotor 1d and disengage its tapered surface 13 from tapered surface 17 of rotor 16. Rotor 19 is raised in small incremental steps in this manner so as to create an increasingly larger air gap between the rotor and stator members. At each increase in the air gap, data is recorded of the above-mentioned characteristics versus the angle of rotation of adjusting screws 26 and 30 so that graphs may be obtained of said data over a range which would include all possible performance requirements of the switch. Subsequently, in a volume production operation, a rotor It? may be assembled in contact with a stator member 16 in the manner explained above, and from the curves obtained in the manner just explained, the adjusting screws 26 and 3% may be turned to obtain the desired air gap which will provide the approximate required electrical characteristics. ln a situation where the electrical characteristics are critical, further testing of the switches in a test set up such as mentioned above may be necessary.

It will be understood from the preceding explanation that the requirement of strict mechanical tolerances on the stator and rotor members is obviated by the construction of this switch because any desired air gap between the stator and rotor readily may be obtained merely by adjusting the axial position of rotor member ill. in this manner, one type of switch having interchangeable parts may be manufactured in volume production and can be assembled so as to produce substantially any desired value of isolation. Although an air gap does exist between the rotor and stator waveguide channels, the leakage energy propagating therebetween is very low. The discs 35 and 36 of dissipative material located on the top and bottom surfaces of rotor 10 help to suppress the leakage energy.

This type of switch obviates the need for supplying or buying switches of different designs, and further obviates the need for the costly machining operation formerly necessary to obtain close mechanical tolerances in highisolation switches. A further advantage of the switch constructed in accordance with this invention is that during operation no axial movement is first necessary in order to disengage the stator and rotor members before the rotor is rotated. The tapered surfaces of the two members permit them to be positioned with such a very small air gap that intimate contact therebetween, or the use of frequency sensitive chokes, is completely unnecessary. The simple ball bearing support provides low friction rotation so that the actuating means for the switch may have minimum power requirements.

It will be noted that nowhere in the switch are there any critical electrical dimensions as there are in the chokes used in prior art switches. For this reason, the switch of this invention is operable over an extremely broad range of frequencies inasmuch as it appears essentially only as a bend in a waveguide transmission path.

It has been found that a switch constructed in accordance with this invention will successfully operate at high power levels despite the fact that an air gap does exist between the rotor and stator members.

An additional factor which makes the switch of this invention attractive is that the switch may be made in a relatively small and compact size since space need not be provided for the chokes commonly used in most pre ent switches.

Any tendency of the rotor to tilt with respect to the central axis of the stator cavity will have negligible er rect on the operation of the switch because the very small air gap obtainable with the switch of this invention will limit such tilting to an extremely small amount. Any contact between the rotor and stator members has been found to be unobjectionable.

While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than limitation and changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

What is claimed is:

l. A waveguide rotary switch for selectively connecting different waveguide channels comprising a stator member having a circularly shaped cavity portion with an inwardly sloping lateral surface, a plurality of waveguide channels radially disposed at respective different angular positions in said stator member and each. having an open end on the sloping surface of said cavity, a frusto-conically-shaped rotor member rotatably disposed within said stator cavity and having an inwardly sloping lateral surface whose angle of inclination is substantially the same as the angle of inclination of the sloping lateral surface of said stator member, at least one waveguide channel in said rotor member for connecting different pairs of said stator waveguide channels when said rotor is rotated to different angular positions, means for supporting said rotor member in an axially and radially non-yielding manner within said stator cavity in spaced relationship with respect to the sloping lateral surface of said stator memher, said axial and radial supporting means comprising first and second end members axially disposed at opposite ends of said rotor member and each thre-adably engaged in said stator member.

2. A rotary waveguide switch for selectively connecting different pairs of angularly disposed waveguide channels comprising a stator member having said waveguide channels disposed therein and having a frnsto-conioally shaped cavity portion therein, said waveguide channels extending radially from said cavity portion and each having an end opening thereon, a frusto-conically shaped rotor member rotatably positioned substantially coaxially within said stator cavity with an air gap separating said two member-s, a waveguide channel extending transversely through said rotor member for substantial registration with difierent pairs of said stator waveguide channels when said rotor is rotated to different angular positions, and axially adjustable supporting means supporting said rotor member in a rotatable, axially non-yielding manner within said stator cavity portion, said axial support means comprising first and second end members axially disposed at opposite ends of said rotor member and each threadably engaged in said stator member, a pair of rigid balls disposed respectively between said end members and respective ends of said rotor, the inner surfiace of said end members being adapted to rotatably support said balls in coaxial alignment, and the end surfaces of said rotor having planar surfaces to make respective point contacts with said balls.

3. A rotary lwaveguide switch for selectively connecting diiferent pairs of angularly disposed waveguide channels comprising a stator member having said waveguide channels disposed therein and having a frusto-conically shaped cavity portion therein, said waveguide channels extending radially from said cavity portion and each having an end opening thereon, a frnsto-conically shaped rotor member positioned substantially coaxially within said stator cavity with a continuous air gap separating the tapered surfaces of said two members, a waveguide channel extending transversely through said rotor member for substantial registration with difierent pairs of said stator waveguide channels when said rotor is rotated to different angular positions, and a pair of axially adjustable ropposed thrust bearings supporting said rotor member in a rotatable, axially and radially non-yielding manner within said stator cavity portion.

4. A rotary waveguide switch for selectively connecting different pairs of angularly disposed Waveguide channels comprising a stator member having said waveguide channels disposed therein and having a trusto-conically shaped cavity portion therein, said waveguide channels extending outwardly from said cavity portion and each having an end opening thereon, a frusto conically shaped rotor member rotatably positioned substantially coaxially within said stator cavity with a continuous :air gap separating the tapered surfaces of said two members, a waveguide channel extending transversely through said rotor member for substantial registration with difierent pairs of said stator waveguide channels when said rotor is rotated to diiferent angular positions, axially adjustable supporting means supporting said rotor member in a rotatable, axially and radially non-yielding manner within said stator cavity portion, and material dissipative to microwave energy disposed on the top and base surfaces of said frusto-conically shaped rotor member [for dissipating leakage microwave energy.

5. A rotary waveguide switch for selectively connecting waveguide channels comprising the combination of a stator member having said waveguide channels disposed therein and having a frusto-conically shaped cavity portion therein, said waveguide channels extending outwardly from said cavity portion and each having an end opening thereon, a rotor member rotatably positioned substan tially coaxially within said stator cavity and having a frusto-conical shape similar to that of the cavity portion of said stator member, a waveguide channel extending transversely through said rotor member for substantial registration with different ones of said stator waveguide channels when said rotor is rotated to different angular positions, and axially-adjustable rotor supporting means disposed at opposite ends of said cavity portion for supporting said rotor member in a rotatable, axially nonyielding manner within said cavity portion, whereby the axial position of the rotor member within said cavity portion of said stator member may be varied by adjustment of said supporting means thereby to vary the separation between the conical surfaces of the rotor and stator members and to maintain a desired separation in a non-yielding manner.

References Cited in the file of this patent UNITED STATES PATENTS 

5. A ROTARY WAVEGUIDE SWITCH FOR SELECTIVELY CONNECTING WAVEGUIDE CHANNELS COMPRISING THE COMBINATION OF A STATOR MEMBER HAVING SAID WAVEGUIDE CHANNELS DISPOSED THEREIN AND HAVIG A FRUSTO-CONICALLY SHAPED CAVITY PORTION THEREIN, SAID WAVEGUIDE CHANNELS EXTENDING OUTWARDLY FROM SAID CAVITY PORTION AND EACH HAVING AN END OPENING THEREON, A ROTOR MEMBER ROTATABLY POSTIONED SUBSTANTIALLY COAXIALLY WITHIN SAID STATOR CAVITY AND HAVING A FRUSTO-CONICAL SHAPE SIMILAR TO THAT OF THE CAVITY PORTION OF SAID STATOR MEMBER, A WAVEGUIDE CHANNEL EXTENDING TRANSVERSELY THROUGH SAID ROTOR MEMBER FOR SUBSTANTIAL REGISTRATION WITH DIFFERENT ONES OF SAID STATOR WAVEGUIDE CHANNELS WHEN SAID ROTOR IS ROTATED TO DIFFERENT ANGULAR POSITIONS, AND AXIALLY-ADJUSTABLE ROTOR SUPPORTING MEANS DISPOSED AT OPPOSITE ENDS OF SAID CAVITY PORTION FOR SUPPORTING SAID ROTOR MEMBER IN A ROTATABLE, AXIALLY NONYIELDING MANNER WITHIN SAID CAVITY PORTION, WHEREBY THE AXIAL POSITION OF THE ROTOR MEMBER WITHIN SAID CAVITY PORTION OF SAID STATOR MEMBER MAY BE VARIED BY ADJUSTMENT OF SAID SUPPORTING MEANS THEREBY TO VARY THE SEPARATION BETWEEN THE CONICAL SURFACES OF THE ROTOR AND STATOR MEMBERS AND TO MAINTAIN A DESIRED SEPARATION IN A NON-YIELDING MANNER. 